This research demonstrates modular battery storage systems' voltage balancing using cascaded H-bridge (CHB) converters. The main principle is to maintain AC-side high-quality power absorption or injection, while on the DC-side independent battery units' voltages get balanced. The CHB converter operates in inversion or rectification modes to discharge the storage system to an AC load/grid, or to charge it from an AC source, respectively. To achieve this goal, several challenges as high-differential mode dv/dt, and dealing with semiconductors voltage drop also arise which should get tackled through feasible controller design. Model predictive control (MPC), as a flexible technique capable of multi-parameter controlling, is used to achieve the beforementioned system objectives in a simple, efficient, and scalable manner. The proposed MPC-based algorithm is an AC current controller, which handles DC-side voltage equalisation and introduces adjacent CHB voltage levels to reduce dv/dt and performs switches voltage loss modelling all in a single control block. An additional linear controller based on multi-carrier pulse width modulation is also implemented for comparison with the MPC-based design. Experimental prototyping and simulation results validate the feasibility of this approach.
Bibliographical noteThis paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright.
The copy of record is available at IET Digital Library.
- Li-ion batteries
- Battery management system
- model predictive control
- voltage balancing